1. Field of the Invention
The invention relates to external storage devices capable of recording and saving various data, a method of producing the external storage devices, an external storage device unit. More specifically, the invention relates to an external storage device exchangeably used for storage equipment and devices as an external storage medium, a method of readily producing the external storage device, and an effective utilization of the external storage device.
2. Description of the Related Art
Storage devices or memory elements, which are capable of recording and saving various data, have been utilized in two systems. In one system they are incorporated and fixed within storage equipment or devices, and in the other system they are releasably or exchangeably incorporated in the storage equipment or devices. For the external storage devices they may optionally be attached or detached or freely removed from the storage equipment or devices, for example, floppy disk devices can be attached and detached by one touch operation. Therefore, when floppy disks are the recording mediums they can separately be used, depending on the purpose and object, to record and save the data, whereby easier data reduction can advantageously be obtained.
However, a problem arises in the floppy disks described above, when the data occasionally disappears during data recording or saving producing less reliability in addition to slower access time. In addition when producing smaller sized floppy disks in response to a miniaturization policy, a storing area of the storage medium is correspondingly smaller to reduce storage capacity, this thus limits practical use thereof.
On the other hand, semiconductor memory devices used as external storage device such as IC memory cards can overcome the drawbacks in floppy disks, because they generally exhibit graded reliability of data recording and saving and relatively rapid access time.
The IC memory cards comprise, a functional circuit in which circuit components containing the semiconductor memory devices or elements are mounted on substrates, a resin casing attached therein with the functional circuit as an inside attachment, a cover for coating and sealing both opening surfaces of the resin casing, and external connection terminals such as two piece connectors which are attached on one edge of the resin casing and electrically connect the functional circuit and the storage equipment/device. However, IC memory cards are assembled with a large amount of components and parts, where a relatively complicated structure is required with limitation to a thickness of the IC memory card. Further, disadvantages arise as a result of lower cost performance or production yields on mass production in addition to the lower releasability for the storage equipment/devices or fluctuated releasability on function.